Continuous process for reducing the molecular weight of ethylene copolymers and ethylene terpolymers

Abstract

A continuous process for reducing the molecular weight of ethylene copolymers and ethylene terpolymers [EP(D)M] comprising the following stages: (a) providing at least one single screw extruder comprising a chamber, a reciprocating single screw mounted within said chamber, wherein said reciprocating single screw is capable of rotating and oscillating within said chamber, said chamber having at least one feed opening and at least one discharge opening, said extruder comprising three conveying and mixing zones, a gear pump, and a submerged die face cutter; (b) feeding at least one ethylene copolymer or ethylene terpolymer [EP(D)M)] into said single screw extruder; (c) conveying the at least one ethylene copolymer or ethylene terpolymer [EP(D)M)] through a first conveying and mixing zone operating at a temperature of from 140°C to 260°C, preferably from 150°C to 250°C, wherein the ethylene copolymer or ethylene terpolymer [EP(D)M)] is uniformly mixed, heated and uniformly softened; (d) conveying the at least one uniformly softened ethylene copolymer or ethylene terpolymer [EP(D)M] exiting the first conveying and mixing zone to a second conveying and mixing zone operating at a temperature of from 220°C to 330°C, preferably from 230°C to 320°C, where the ethylene copolymer or ethylene terpolymer [EP(D)M] is further mixed, heated and partially decomposed; (e) conveying the at least one partially decomposed ethylene copolymer or ethylene terpolymer [EP(D)M] exiting the second conveying and mixing zone to a third conveying and mixing zone operating at a temperature of from 170°C to 340°C, preferably from 180°C to 330°C, where the ethylene copolymer or ethylene terpolymer [EP(D)M] is further mixed, heated and further decomposed; (f) conveying the at least one further cracked ethylene copolymer or ethylene terpolymer [EP(D)M)] exiting the third conveying and mixing zone to the gear pump operating at a temperature of from 170°C to 340°C, preferably from 180°C to 330°C, wherein the ethylene copolymer or ethylene terpolymer [EP(D)M)] is further cracked; (g) recovering said at least one further cracked ethylene copolymer or ethylene terpolymer [EP(D)M)] exiting said underwater die face cutter; A continuous process comprising: The ethylene copolymers and ethylene terpolymers [EP(D)M] obtained by the above process can be advantageously used as viscosity index improvers (VII) for lubricating oils.

Description

[Technical Field]

[0001] The present invention relates to a continuous process for reducing the molecular weight of ethylene copolymers and terpolymers [EP(D)M].

[0002] More specifically, the present invention relates to a continuous process for reducing the molecular weight of ethylene copolymers and ethylene terpolymers [EP(D)M] which involves the use of a single screw extruder equipped with a piston screw ("reciprocating single screw"), three conveying and mixing zones, a gear pump, and a submerged die face cutter, wherein said three conveying and mixing zones and said gear pump are operated within specific temperature ranges.

[0003] The ethylene copolymers and ethylene terpolymers [EP(D)M] obtained by the above process can be advantageously used as viscosity index improvers (VII) for lubricating oils. [Background technology]

[0004] Ethylene copolymers and terpolymers [EP(D)M] are widely used in the field of lubricating oil additives (also known in the industry as olefin copolymers (OCPs)) as viscosity index improvers (VII) to adjust the viscosity of lubricating oils over temperature.

[0005] Micro / macrostructure, weight average molecular weight (M) of ethylene copolymer and ethylene terpolymer [EP(D)M] w ), polydispersity index (PDI), i.e., weight average molecular weight (M w ) and number average molecular weight (M n ) and the ratio (M w / M n), as well as the amount of ethylene copolymers and ethylene terpolymers [EP(D)M)] used, are all factors that modify the effectiveness of the ethylene copolymers and ethylene terpolymers as viscosity index improvers (VII) for lubricating oils and the final properties of the formulations in which they are used.

[0006] Optimization of the micro / macrostructure of ethylene copolymers and ethylene terpolymers [EP(D)M] allows finding the right balance to achieve the desired technological parameters.

[0007] Furthermore, low molecular weight is essential for the application performance of viscosity index improvers (VII) in lubricating oils, and the processes typically used to manufacture ethylene copolymers and terpolymers (EP(D)M) (solution or slurry processes) often provide ethylene copolymers and terpolymers (EP(D)M) with very high molecular weights, which necessitates subjecting these ethylene copolymers and terpolymers (EP(D)M) to a thermal cracking process.

[0008] For example, European Patent No. 1013673 relates to a process for reducing the molecular weight of a polymeric material selected from ethylene copolymers and ethylene terpolymers [EP(D)M)] or mixtures thereof. The process involves treating the polymeric material with at least one hydroperoxide present in an amount sufficient to cause molecular weight reduction at a temperature of 80°C to 250°C, wherein the ethylene copolymers and ethylene terpolymers [EP(D)M)] have a molar propylene content of 16% to 50%. The resulting ethylene copolymers and ethylene terpolymers [EP(D)M] are said to have several uses, including use as viscosity index improvers (VII) for lubricating oils and as modifiers for high-flow plastics. The above process can be carried out in an extruder, preferably a twin-screw extruder.

[0009] European Patent No. 1671982 relates to a process for producing a viscosity index improver (VII) that has improved dimensional stability and can improve the rheology of low-temperature lubricating oils. The process involves treating a mixture of linear polyethylene, an ethylene homopolymer or copolymer characterized by a crystalline structure and a density of 0.88 to 0.94, with amorphous ethylene copolymers and ethylene terpolymers [EP(D)M], optionally blended with semi-crystalline ethylene copolymers and ethylene terpolymers [EP(D)M]. The treatment is carried out in an extruder, in the presence of one or more substances of hydroperoxidic nature and, optionally, in the presence of a polyfunctional vinyl monomer in an amount of 0 to 2% by weight. The treatment is carried out for 100 seconds. -1 and at temperatures between 75°C and 260°C, and the amorphous ethylene copolymers and terpolymers [EP(D)M] are characterized by an ethylene content between 35% and 62% by weight and a third monomer content between 0% and 10% by weight. The above process can be carried out in an extruder, preferably a twin-screw extruder.

[0010] EP 1632504 relates to a process for the preparation of a viscosity index improver (VII), which comprises treating under high shear conditions a composition comprising (i) one or more ethylene copolymers or ethylene terpolymers [EP(D)M)] and (ii) one or more polyvinylarylene / hydrogenated conjugated diene / polyvinylarylene block copolymers, the weight ratio of (i) / (ii) being between 98 / 2 and 80 / 20, at a temperature between 150°C and 400°C for a time not exceeding 150 seconds, for a period of 75 seconds. -1 The above process can be carried out in an extruder, preferably a twin-screw extruder.

[0011] European Patent No. 1984479 is 50 seconds -1 Under shear conditions of (i) one or more ethylene copolymers or ethylene terpolymers [EP(D)M)]; (ii) one or more polyvinylarylene / hydrogenated conjugated diene / polyvinylarylene block copolymers; (iii) lubricating oil; wherein (ii) is present at a concentration of 1.5 wt % to 20 wt % and (iii) is present at a concentration of 1.5 wt % to 45 wt %.

[0012] The above process can be carried out in an extruder, preferably a twin-screw extruder.

[0013] Canadian Patent No. 991792 relates to a continuous process for producing lubricating oil additives by pyrolyzing in an extruder under non-oxidizing conditions a substantially linear, high molecular weight amorphous ethylene-propylene hydrocarbon copolymer containing 25% to 50% by weight of polymerized propylene, 0% to 5% by weight of polymerized non-conjugated hydrocarbon diene, and the balance polymerized ethylene. The process includes uniformly mixing and heating the copolymer in an initial zone at a temperature of about 150°C to 280°C, below the decomposition temperature of the copolymer, until the copolymer is uniformly molten; passing the molten copolymer through a second zone, where it is uniformly mixed and heated to a temperature of about 300°C to 500°C, until a decomposed copolymer is obtained having an intrinsic viscosity, measured at 30°C on a solution of 0.1 g of copolymer in 100 ml of tetrachloroethylene, lower than that of the starting copolymer and ranging from 0.1 dL / g to 1.8 dL / g, and a molecular weight distribution substantially less than or equal to that of the starting copolymer; removing the decomposed copolymer from the second zone; and cooling and recovering the decomposed copolymer, which is substantially colorless or white and contains only traces of oil-insoluble material.

[0014] However, each of the above processes may have some drawbacks. For example, to obtain ethylene copolymers and ethylene terpolymers [EP(D)M] with molecular weights suitable for use as viscosity index improvers (VII), the use of hydroperoxides or operation at high temperatures (up to 500°C) may be required, which may require operation in an inert atmosphere (e.g., in the presence of nitrogen) and may lead to gel formation and branching in the final product. Furthermore, to improve the dimensional stability of the resulting ethylene copolymers and ethylene terpolymers [EP(D)M], the use of small amounts of polyvinylarylene / hydrogenated conjugated diene / polyvinylarylene block copolymers or multifunctional vinyl monomers may be required. Summary of the Invention

[0015] The Applicant therefore set out to solve the problem of finding a continuous process for reducing the molecular weight of ethylene copolymers and ethylene terpolymers [EP(D)M] that can be advantageously used as viscosity index improvers (VII) for lubricating oils and that overcomes the above-mentioned drawbacks.

[0016] Applicant has devised a continuous process for reducing the molecular weight of ethylene copolymers and ethylene terpolymers [EP(D)M], which includes the use of a single-screw extruder equipped with a reciprocating single screw, three conveying and mixing zones, a gear pump, and a submerged die face cutter, wherein the three conveying and mixing zones and the gear pump operate within a specific temperature range. In particular, Applicant has discovered that by using the single-screw extruder, it is possible to obtain ethylene copolymers and ethylene terpolymers [EP(D)M] having molecular weights suitable for use as viscosity index improvers (VII) in the absence of hydroperoxides, while operating at temperatures lower than those of the prior art to avoid both operation under an inert atmosphere and the formation of gels and branches in the final product. Furthermore, the process does not require the use of polyvinylarylene / hydrogenated conjugated diene / polyvinylarylene block copolymers or multifunctional vinyl monomers to improve the dimensional stability of the final product.

[0017] The object of the present invention is therefore a continuous process for reducing the molecular weight of ethylene copolymers and ethylene terpolymers [EP(D)M], comprising the following stages: (a) providing at least one single screw extruder comprising a chamber, a reciprocating single screw mounted within said chamber, wherein said reciprocating single screw is capable of rotating and oscillating within said chamber, said chamber having at least one feed opening and at least one discharge opening, said extruder comprising three conveying and mixing zones, a gear pump, and a submerged die face cutter; (b) feeding at least one ethylene copolymer or ethylene terpolymer [EP(D)M)] into said single screw extruder; (c) conveying the at least one ethylene copolymer or ethylene terpolymer [EP(D)M)] through a first conveying and mixing zone operating at a temperature of from 140°C to 260°C, preferably from 150°C to 250°C, wherein the ethylene copolymer or ethylene terpolymer [EP(D)M)] is uniformly mixed, heated and uniformly softened; (d) conveying the at least one uniformly softened ethylene copolymer or ethylene terpolymer [EP(D)M] exiting the first conveying and mixing zone to a second conveying and mixing zone operating at a temperature of from 220°C to 330°C, preferably from 230°C to 320°C, where the ethylene copolymer or ethylene terpolymer [EP(D)M] is further mixed, heated and partially decomposed; (e) conveying the at least one partially decomposed ethylene copolymer or ethylene terpolymer [EP(D)M] exiting the second conveying and mixing zone to a third conveying and mixing zone operating at a temperature of from 170°C to 340°C, preferably from 180°C to 330°C, where the ethylene copolymer or ethylene terpolymer [EP(D)M] is further mixed, heated and further decomposed; (f) conveying the at least one further cracked ethylene copolymer or ethylene terpolymer [EP(D)M)] exiting the third conveying and mixing zone to the gear pump operating at a temperature of from 170°C to 340°C, preferably from 180°C to 330°C, wherein the ethylene copolymer or ethylene terpolymer [EP(D)M)] is further cracked; (g) recovering said at least one further cracked ethylene copolymer or ethylene terpolymer [EP(D)M)] exiting said underwater die face cutter; and (c) providing a continuous process comprising:

[0018] For purposes of this specification and the claims that follow, definitions of numerical ranges always include the endpoints unless otherwise specified.

[0019] For purposes of this specification and the claims that follow, the term "comprising" also includes the terms "which essentially consists of" or "which consists of."

[0020] For the purposes of the present invention, a single screw extruder equipped with a reciprocating single screw, three conveying and mixing zones, a gear pump, and an underwater die face cutter, and also having the following characteristics, can be used: - for conventional single-screw extruders in which the screw is continuous helical, said reciprocating single screw has threads interrupted at intervals of 120° in the radial direction, and pins or teeth associated with these threads are inserted into the barrel; - compared to a conventional single screw extruder in which the screw movement is only rotational, the movement of the reciprocating single screw is rotational and oscillating, in fact, the rotation of the reciprocating single screw is superimposed with an oscillation (or axial stroke), resulting in an improved mixing and decomposition capacity within the extruder; - the frequency of said axial motion ("reciprocating movement") is the same as the rotational speed, and a gear system causes a complete forward and backward stroke for each revolution of said reciprocating uniaxial screw; - The amplitude of vibration is approximately 20 mm; - during the execution of the complete forward and retraction strokes mentioned above, the path followed by the pins (or teeth) covers and cleans the entire surface of the reciprocating screw so that there are no areas where material can stagnate, and in fact the threads ("kneading flights") oscillate around the pins (or teeth), which allows a very uniform velocity gradient between the threads ("kneading flights") and the pins; - the combined rotational and axial motion of the reciprocating single screw creates an extensional flow with a strong dispersive mixing action between the threads ("kneading flights") and the pins; - the melting of the ethylene copolymer or ethylene terpolymer [EP(D)M] occurs in the gap between the thread ("kneading flight") and the pin; - Due to said improved mixing ability, the ethylene copolymer or ethylene terpolymer [EP(D)M] does not exhibit heterogeneity in the sense of solid and molten parts, but rather the ethylene copolymer or ethylene terpolymer [EP(D)M] melts simultaneously, resulting in high viscosity and generating high shear stress values, especially in the first two mixing zones.

[0021] More details about the single-screw extruder are found, for example, in Elemans PHM and Mejer HEH, "Polymer Engineering and Science" (1990), Mid-August, Vol. 30, No. 15, pp. 893-904.

[0022] According to a preferred embodiment of the present invention, the single screw extruder operates at a screw speed of 220 rpm to 300 rpm, preferably at a screw speed of 230 rpm to 280 rpm.

[0023] According to a preferred embodiment of the present invention, the single screw extruder operates at a flow rate of between 300 kg / h and 700 kg / h, preferably between 400 kg / h and 600 kg / h.

[0024] After leaving the underwater die face cutter, the cracked ethylene copolymer or ethylene terpolymer [EP(D)M] is in the form of "pellets" which are separated from the water, for example by centrifugation, and subsequently sent by pneumatic conveying to the drying and packaging section.

[0025] According to a preferred embodiment of the present invention, the ethylene copolymer or ethylene terpolymer [EP(D)M] is - 20% to 90% by weight, preferably 40% to 85% by weight, of ethylene relative to the total weight of the ethylene copolymer or ethylene terpolymer [EP(D)M)]; - 10% to 80% by weight, preferably 15% to 60% by weight, of propylene relative to the total weight of the ethylene copolymer or ethylene terpolymer [EP(D)M)]; - from 0% to 12% by weight, preferably from 0% to 5% by weight, of a non-conjugated diene relative to the total weight of the ethylene copolymer or ethylene terpolymer [EP(D)M)], Includes:

[0026] According to a preferred embodiment of the present invention, the ethylene copolymer or ethylene terpolymer [EP(D)M] has the following characteristics: a weight average molecular weight (M) of 115,000 Da to 500,000 Da, preferably 120,000 Da to 450,000 Da, more preferably 125,000 Da to 250,000 Da; w ); - a polydispersity index (PDI), i.e., a weight average molecular weight (M w ) and number average molecular weight (M n ) and the ratio (M w / M n ), It has.

[0027] According to a preferred embodiment of the present invention, the non-conjugated diene optionally present is, for example: - non-conjugated linear dienes such as 1,4-hexadiene, 1,6-octadiene; - non-conjugated branched acyclic dienes such as 5-methyl-1,4-hexadiene, 3,7-dimethyl-1,6-octadiene, 3,7-dimethyl-1,7-octadiene; - non-conjugated monocyclic alicyclic dienes such as 1,4-cyclohexadiene, 1,5-cyclooctadiene, 1,5-cyclododecadiene; - Methyltetrahydroindene, dicyclopentadiene, bicyclo[2.2.1]hepta-2,5-diene, C1-C8-alkenyl-norbornenes, C2-C8-alkylidene-norbornenes, C3-C 12 -Cyclo-alkenyl-norbornenes, C3-C 12- non-conjugated dienes with fused or bridged alicyclic rings, such as cycloalkylidene-norbornenes, for example 5-methylene-2-norbornene, 5-ethylidene-2-norbornene (ENB), 5-propenyl-2-norbornene, Preferably, the non-conjugated diene is 5-ethylidene-2-norbornene (ENB).

[0028] Both amorphous and semi-crystalline ethylene copolymers or terpolymers [EP(D)M], alone or in mixtures with one another, can be used advantageously for the purposes of the process of the present invention.

[0029] Ethylene copolymers and ethylene terpolymers [EP(D)M] that can be advantageously used for the purposes of the present invention and that are currently commercially available are the Dutral® CO products by Versalis.

[0030] The ethylene copolymers and ethylene terpolymers [EP(D)M)] obtained by the above process have the following characteristics: - a weight average molecular weight (M) of 50,000 Da to 140,000 Da, preferably 75,000 Da to 120,000 Da; w ); - a polydispersity index (PDI), i.e., a weight average molecular weight (M w ) and number average molecular weight (M n ) and the ratio (M w / M n ); - Thickening power (TP) of 4cSt to 7cSt; - Shear Stability Index (SSI) of 20% to 30%, It has.

[0031] The aforementioned ethylene copolymers and ethylene terpolymers [EP(D)M] can be advantageously used as viscosity index improvers (VII) for lubricating oils.

[0032] Preferably, the aforementioned ethylene copolymers and ethylene terpolymers [EP(D)M)] can be used in lubricating oils selected from mineral base oils or synthetic base oils.

[0033] Therefore, a further object of the present invention is the use of the ethylene copolymers and ethylene terpolymers obtained by the process according to the invention as viscosity index improvers (VII) for lubricating oils, said lubricating oils being preferably selected from mineral base oils or from synthetic base oils. [Brief explanation of the drawings]

[0034] [Figure 1] FIG. 1 below shows, for illustrative and non-limiting purposes, an embodiment of the process object of the present invention and a block diagram of the plant and single screw extruder used in said process.

[0035] Specifically, in Figure 1, ethylene copolymer or ethylene terpolymer [EP(D)M] (1) is fed through a feed hopper to a single-screw extruder equipped with three conveying and mixing zones, a gear pump, and a submerged die face cutter, with the three conveying and mixing zones and the gear pump operating within a specific temperature range. Specifically, the ethylene copolymer or ethylene terpolymer [EP(D)M] (1) is uniformly mixed, heated, and uniformly softened through the first conveying and mixing zone to obtain ethylene copolymer or ethylene terpolymer [EP(D)M] (2). This is conveyed to the second conveying and mixing zone, where it is further mixed, heated, and partially decomposed to obtain partially decomposed ethylene copolymer or ethylene terpolymer [EP(D)M] (3). This is conveyed to the third conveying and mixing zone, where it is further mixed, heated, and further decomposed to obtain further decomposed ethylene copolymer or ethylene terpolymer [EP(D)M] (4). This is conveyed to a gear pump to obtain further cracked ethylene copolymer or ethylene terpolymer [EP(D)M] (5), which is recovered at the outlet from the underwater die face cutter in the form of "pellets" that are separated from the water, for example by centrifugation, and subsequently sent by pneumatic conveying to the drying and packaging section.

[0036] For a better understanding of the present invention and for putting it into practice, some illustrative, non-limiting examples are reported below.

[0037] The analytical and characterization methods reported below were used.

[0038] 13 C-NMR and 1 H-NMR spectrum 13 C-NMR and 1 H-NMR spectra were recorded at 120°C on a variable temperature nuclear magnetic resonance spectrometer model Bruker Avance 300 equipped with a 10 mm probe.

[0039] For this purpose, polymer solutions of degraded ethylene copolymers and ethylene terpolymers [EP(D)M)] obtained by the process of the present invention were used, which had a concentration of 10%-15% w / v (g / mL) prepared with deuterated tetrachloroethane (C2D2Cl4) at 120 °C and with tetramethylsilane (TMS) as an internal standard.

[0040] The structures (i.e., ethylene (%), propylene (%), and any non-conjugated diene content) of the decomposed ethylene copolymers and ethylene terpolymers [EP(D)M)] obtained by the process of the present invention were identified by analyzing the above spectra based on the content reported in the literature by Di Martino S. and Kelchtermans M., "Journal of Applied Polymer Science" (1995), Vol. 56, Issue 13, pp. 1781-1787 (Method No. 3, page 1784).

[0041] Molecular weight determination The weight average molecular weight (M) of the degraded ethylene copolymers and ethylene terpolymers [EP(D)M] obtained by the process object of the present invention w ), number average molecular weight (M n ), and ratio M w / M n The determination of the polydispersity index (PDI) corresponding to the hydroxybenzoates was carried out by GPC ("gel permeation chromatography") using an integrated instrument HT-GPC PL220 by Agilent Technologies with three detection lines: refractive index ("IR"), viscometer ("VS"), and dual angle laser light scattering ("DALLS"), operated under the following conditions: - a precolumn (guard column) with dimensions 50 x 7.5 mm and a particle size of 10 μm; - three GPC columns from Agilent Technologies with dimensions 300 x 7.5 mm and mixed porous particle size 10 μm; - Mettler XPR225 analytical balance; - Laboratory glassware; - Distillation and degassing systems for solvent recovery; - 50ml automatic dispensing device; - pL-SP-260 Automated Dissolution Apparatus by Agilent Technologies; - Column injection temperature: 135°C; - Temperature of column and detection line: 135°C; - Solvent / eluent: 1,2-dichlorobenzene (HPLC grade, 99+% - Acros Organics™); - Flow rate: 1ml / min; - Calculation of molecular weight using universal calibration curve.

[0042] These operating conditions were continuously monitored using a personal computer equipped with Agilent GPC / SEC software from Agilent Technologies.

[0043] The calibration was carried out as follows:

[0044] The nominal peak molecular weight (M) was used to determine the interdetector delay (IDD) and calibration constants for the four signals (RID, VS, LS15°, and LS90°). p ) A solution of 1,2-dichlorobenzene (HPLC grade, 99+% - Acros Organics™) containing 100 kDa polystyrene (PS) standards was prepared.

[0045] Each has a different nominal peak molecular weight (M p Seven solutions of 1,2-dichlorobenzene (HPLC grade, 99+% - Acros Organics™) containing 1,2-dichlorobenzene (HPLC grade, 99+% - Acros Organics™) and two monodisperse polystyrene (PS) standards of different concentrations were also prepared, the molecular weights being chosen so that the chromatographic elution peaks were well separated, while the concentration of each standard was chosen inversely proportional to the molecular weight. The different nominal peak molecular weights (M p) ranged from 2 kDa to 7000 kDa.

[0046] Each solution was prepared at room temperature (25°C) under stirring in the PL-SP-260 automated dissolver from Agilent Technologies described above.

[0047] The calibration curve was calculated using a third-order polynomial function using a personal computer equipped with the aforementioned Agilent GPC / SEC software from Agilent Technologies.

[0048] Identification of thickening power (TP) Thickening power (TP) was determined according to ASTM D7042-04.

[0049] Determination of Shear Stability Index (SSI) The shear stability index (SSI) was determined according to ASTM D7109-12. [Example]

[0050] Example 1 (invention) - 54% by weight of ethylene; - 46% by weight of propylene; - Weight average molecular weight (M) of 190,000 Da w ); - Polydispersity index (PDI) of 2.2, An amorphous ethylene propylene copolymer Dutral® CO 058 (Versalis) having the formula: was fed at a rate of 500 kg / h to a single-screw extruder (BUSS MDK 140 by Aaron Equipment) with a reciprocating screw, a diameter of 140 mm, a length (L) to diameter (D) ratio (L / D) of 11, three conveying and mixing zones, a gear pump, and an underwater die face cutter, under the following conditions: - Screw rotation speed: 260 rpm; - Temperature profile 1st zone: 160℃~210℃; - Temperature profile 2nd zone: 270℃~310℃; - Temperature profile 3rd zone: 280℃~320℃; - Gear pump temperature: 280℃~320℃, It worked.

[0051] After discharge from the underwater die face cutter (cutting speed is 2700 rpm), the cracked and cooled copolymer is recovered in the form of "pellets", separated from the water by centrifugation, and then sent by pneumatic conveying to the drying and packaging section.

[0052] The resulting degraded copolymer was subjected to NMR and GPC ("gel permeation chromatography") analysis, operating as described above, giving the following values: - 54% by weight of ethylene; - 46% by weight of propylene; - Weight average molecular weight (M) of 80,000 Da w ); - Polydispersity index (PDI) of 2.2.

[0053] Example 2 (invention) - 68% by weight of ethylene; - 32% by weight of propylene; - Weight average molecular weight (M) of 130,000 Da w ); - Polydispersity index (PDI) of 2.2, 70% by weight of a semi-crystalline ethylene propylene copolymer Dutral® CO 034 (Versalis) having the following characteristics: 30% by weight of an amorphous ethylene propylene copolymer Dutral® CO 058 (Versalis) having the above characteristics, The mixture was fed at a rate of 500 kg / h to a single-screw extruder (BUSS MDK 140 by Aaron Equipment) with a reciprocating screw, a diameter of 140 mm, a length (L) to diameter (D) ratio (L / D) of 11, three conveying and mixing zones, a gear pump, and an underwater die face cutter, operated under the following conditions: - Screw rotation speed: 280 rpm; - Temperature profile 1st zone: 180℃~240℃; - Temperature profile 2nd zone: 250℃~300℃; - Temperature profile 3rd zone: 190℃~300℃, - Gear pump temperature: 190℃~300℃, It worked.

[0054] After discharge from the underwater die face cutter (cutting speed is 2700 rpm), the cracked and cooled copolymer is recovered in the form of "pellets", separated from the water by centrifugation, and then sent by pneumatic conveying to the drying and packaging section.

[0055] The resulting degraded copolymer was subjected to NMR and GPC ("gel permeation chromatography") analysis, operating as described above, giving the following values: - 63.5% by weight of ethylene; - 36.5% by weight of propylene; - Weight average molecular weight (M) of 85,000 Da w ); - Polydispersity index (PDI) of 2.2.

[0056] Example 3 (Comparative Example) - 54% by weight of ethylene; - 46% by weight of propylene; - Weight average molecular weight (M) of 190,000 Da w ); - Polydispersity index (PDI) of 2.2, The amorphous ethylene propylene copolymer Dutral® CO 058 (Versalis) having the formula: was fed at a flow rate of 1 kg / h into a single-screw extruder (Goettfert 20D by Goettfert GmbH) with a diameter of 2 mm, a length (L) to diameter (D) ratio (L / D) of 20, three conveying and mixing zones, and a die, without a reciprocating screw, under the following conditions: - Screw rotation speed: 100 rpm; - Temperature profile 1st zone: 160℃~180℃; - Temperature profile 2nd zone: 290℃~310℃; - Temperature profile 3rd zone: 300℃~320℃; - cooling in a water bath, It worked.

[0057] After exiting the die, the cracked and cooled copolymer was collected in the form of air-dried "spaghetti."

[0058] The copolymer obtained was subjected to NMR and GPC ("gel permeation chromatography") analysis, operating as described above, giving the following values: - 54% by weight of propylene; - 46% by weight of ethylene; - weight average molecular weight (Mw) of 150,000 Da; - Polydispersity index (PDI) of 2.2.

[0059] Example 4 (Comparative Example) - 68% by weight of ethylene; - 32% by weight of propylene; - Weight average molecular weight (M) of 130,000 Da w ); - Polydispersity index (PDI) of 2.2, 70% by weight of a semi-crystalline ethylene propylene copolymer Dutral® CO 034 (Versalis) having the following characteristics: 30% by weight of an amorphous ethylene propylene copolymer Dutral® CO 058 (Versalis) having the above characteristics, The mixture was fed at a flow rate of 1 kg / h into a single-screw extruder (Goettfert 20D by Goettfert GmbH) with a diameter of 2 mm, a length (L) to diameter (D) ratio (L / D) of 20, three conveying and mixing zones and a die, and no reciprocating screw, under the following conditions: - Screw rotation speed: 100 rpm; - Temperature profile 1st zone: 160℃~180℃; - Temperature profile: 2nd zone: 270℃~300℃; - Temperature profile 3rd zone: 290℃~320℃; - cooling in a water bath, It worked.

[0060] After exiting the die, the cracked and cooled copolymer was collected in the form of air-dried "spaghetti."

[0061] The copolymer obtained was subjected to NMR and GPC ("gel permeation chromatography") analysis, operating as described above, giving the following values: - 63.5% by weight of propylene; - 36.5% by weight of ethylene; - Weight average molecular weight (M) of 160,000 Da w ); - Polydispersity index (PDI) of 2.2.

[0062] Example 5 (invention) Evaluation as a viscosity index improver for lubricating oils (VII) For this purpose, the degraded ethylene propylene copolymers (EPR) obtained in Examples 1 (invention), 2 (invention), 3 (comparison) and 4 (comparison) were dissolved in an amount of 1% by weight in the reference base oil SN 150 Group I (Eni SpA).

[0063] The resulting solutions were used to determine the thickening power (TP) according to ASTM D7402-04 and the shear stability index (SSI) according to ASTM D7109-12, as listed above, and the results are shown in Table 2.

[0064] SN 150 base oil has the following characteristics: - Kinematic viscosity (KV) at 100°C of 5.3 cSt; - Pour point of -15°C. [Table 1]

[0065] The data in Table 2 show that ethylene-propylene copolymers (EPRs) obtained using a non-reciprocating single-screw extruder [Example 3 (Comparative) and Example 4 (Comparative)] do not provide the desired results when used as viscosity index improvers.

Claims

1. A continuous process for reducing the molecular weight of ethylene copolymers and ethylene terpolymers [EP(D)M] comprising the following stages: (a) providing at least one single screw extruder comprising a chamber, a reciprocating single screw mounted within said chamber, wherein said reciprocating single screw is capable of rotating and oscillating within said chamber, said chamber having at least one feed opening and at least one discharge opening, said extruder comprising three conveying and mixing zones, a gear pump, and an underwater die face cutter; (b) feeding at least one ethylene copolymer or ethylene terpolymer [EP(D)M)] into said single screw extruder; (c) conveying said at least one ethylene copolymer or ethylene terpolymer [EP(D)M)] through a first conveying and mixing zone operating at a temperature of from 140°C to 260°C, preferably from 150°C to 250°C, wherein said ethylene copolymer or ethylene terpolymer [EP(D)M)] is uniformly mixed, heated and uniformly softened; (d) conveying the at least one uniformly softened ethylene copolymer or ethylene terpolymer [EP(D)M] exiting the first conveying and mixing zone to a second conveying and mixing zone operating at a temperature of from 220°C to 330°C, preferably from 230°C to 320°C, where the ethylene copolymer or ethylene terpolymer [EP(D)M] is further mixed, heated and partially decomposed; (e) conveying said at least one partially decomposed ethylene copolymer or ethylene terpolymer [EP(D)M] exiting said second conveying and mixing zone to a third conveying and mixing zone operating at a temperature of from 170°C to 340°C, preferably from 180°C to 330°C, wherein said ethylene copolymer or ethylene terpolymer [EP(D)M] is further mixed, heated and further decomposed; (f) conveying said at least one further cracked ethylene copolymer or ethylene terpolymer [EP(D)M)] exiting said third conveying and mixing zone to said gear pump operating at a temperature of from 170°C to 340°C, preferably from 180°C to 330°C, wherein said ethylene copolymer or ethylene terpolymer [EP(D)M)] is further cracked; (g) recovering said at least one further cracked ethylene copolymer or ethylene terpolymer [EP(D)M)] exiting said underwater die face cutter; A continuous process comprising:

2. 2. A continuous process for reducing the molecular weight of ethylene copolymers and terpolymers [EP(D)M)] according to claim 1, wherein the single screw extruder operates at a rotation speed of the screw of from 220 rpm to 300 rpm, preferably from 230 rpm to 280 rpm.

3. 3. A continuous process for reducing the molecular weight of ethylene copolymers and ethylene terpolymers [EP(D)M)] according to claim 1 or claim 2, wherein the single screw extruder operates at a flow rate of from 300 kg / h to 700 kg / h, preferably from 400 kg / h to 600 kg / h.

4. The ethylene copolymer or ethylene terpolymer [EP(D)M)] is - from 20% to 90% by weight, preferably from 40% to 85% by weight, of ethylene relative to the total weight of said ethylene copolymer or ethylene terpolymer [EP(D)M)]; - from 10% to 80% by weight, preferably from 15% to 60% by weight, of propylene relative to the total weight of said ethylene copolymer or ethylene terpolymer [EP(D)M)]; - from 0% to 12% by weight, preferably from 0% to 5% by weight, of a non-conjugated diene relative to the total weight of said ethylene copolymer or ethylene terpolymer [EP(D)M)], 4. A continuous process for reducing the molecular weight of ethylene copolymers and ethylene terpolymers [EP(D)M)] according to any one of claims 1 to 3, comprising:

5. The ethylene copolymer or ethylene terpolymer [EP(D)M)] has the following characteristics: a weight average molecular weight (Mw) of from 115,000 Da to 500,000 Da, preferably from 120,000 Da to 450,000 Da, more preferably from 125,000 Da to 250,000 Da; - a polydispersity index (PDI), i.e., a weight average molecular weight (M), of less than 5, preferably between 1.8 and 4.5, more preferably between 1.9 and 3.5; ｗ ) and number average molecular weight (M ｎ ) and the ratio (M ｗ / M ｎ ), 5. A continuous process for reducing the molecular weight of ethylene copolymers and terpolymers [EP(D)M)] according to any one of claims 1 to 4, comprising:

6. The non-conjugated diene optionally present is: - non-conjugated linear dienes such as 1,4-hexadiene, 1,6-octadiene; non-conjugated branched acyclic dienes such as 5-methyl-1,4-hexadiene, 3,7-dimethyl-1,6-octadiene, 3,7-dimethyl-1,7-octadiene; - non-conjugated monocyclic alicyclic dienes such as 1,4-cyclohexadiene, 1,5-cyclooctadiene, 1,5-cyclododecadiene; - methyltetrahydroindene, dicyclopentadiene, bicyclo[2.2.1]hepta-2,5-diene, C １ ~C ８ -alkenyl-norbornene, C ２ ~C ８ -Alkylidene-norbornene, C ３ ~C １２ -cyclo-alkenyl-norbornene, C ３ ~C １２ - cycloalkylidene-norbornenes, for example, non-conjugated dienes with fused or bridged alicyclic rings, such as 5-methylene-2-norbornene, 5-ethylidene-2-norbornene (ENB), 5-propenyl-2-norbornene, etc.; 5. A continuous process for reducing the molecular weight of ethylene copolymers and terpolymers [EP(D)M)] according to claim 4, wherein the non-conjugated diene is selected from the group consisting of 5-ethylidene-2-norbornene (ENB).

7. Use of ethylene copolymers and ethylene terpolymers [EP(D)M)] obtained by the process according to any one of claims 1 to 6 as viscosity index improvers (VII) for lubricating oils, said lubricating oils being preferably selected from mineral base oils or from synthetic base oils.

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